The Orokonui Ecosanctuary is set to hold its first cross-country on April 22, which is also Earth Day.
It will involve runners completing an 18.5km track around the sanctuary and includes an overall 370m climb.
The course covers beach, forest and estuary terrains and is expected to be reasonably challenging.
"It’s quite a challenging route and to incorporate those different features, we needed to make it that long," race organiser Chris Baillie said.
"It’s kind of like a half-marathon. We wanted to attract serious runners. We thought they’d really enjoy it.
"My brother’s a keen runner, so he ran it for me and said it was a good challenge and said it would be great."
She said it was important the entrants were serious runners, as there was a time constraint on the event due to the tide.
Entries would be capped at 100 this year, with a $50 entry fee being used to raise money for the ecosanctuary.
Baillie said entries were going well, although there were still plenty of open spaces. She was confident they would fill up the spots by the time of the race.
For those who were not serious runners there was an 11km course that could be run or walked.
Baillie hopes the race may be expanded in the years to come.
"This is the first one and we’ll definitely do it every year.
"We’ve had really good registrations so far, so the interest is out there.
"We were trying to fit in with the Wild Dunedin festival and Earth Day.
"But next year we’ll try and fit in with some other runs, maybe a bit earlier in the year."
There would be prizes for the first-placed man and women, as well as for winners of the masters grades.
